This application claims the priority of the commonly owned copending German patent application Serial No. 101 08 875.2 filed Feb. 23, 2001. The disclosure of such commonly owned copending patent application, as well as of that of each US and foreign patent and patent application identified in the specification of the present application, is incorporated herein by reference.
The present invention relates to improvements in clutch discs (also called clutch plates) which are utilized in friction clutches to transmit torque between rotary driving and driven parts. Examples of systems which employ friction clutches are power trains of motor vehicles wherein a friction clutch is engageable to transmit torque between the output shaft (such as a crankshaft or a camshaft) of an engine or another prime mover and the input shaft of a change-speed transmission. The clutch disc of the friction clutch in such power trains is arranged to transmit torque between a counter-pressure plate receiving torque from an engine-driven output shaft and the input shaft of the transmission when the clutch is at least partly engaged. Such engagement normally involves causing a suitable spring (such as a diaphragm spring) to push an axially movable pressure plate against the clutch disc and to thus maintain the clutch disc in a more or less pronounced frictional engagement with the counterpressure plate.
A standard clutch disc comprises a hub which is non-rotatably connectable with a rotary driven shaft, at least one washer-like carrier which is affixed to or forms part of and surrounds the hub, and two annular friction linings or facings borne by the radially outer-most portion of the carrier. When the friction clutch is engaged, one of the friction linings is in frictional contact with the counterpressure plate and the other lining is engaged by the pressure plate. It is also customary to employ a resilient lining carrier between the two friction linings. Friction clutches of the just outlined character are disclosed, for example, in published German patent application No. 30 23 634, in German patent No. 27 20 664, in published German patent application No. 26 41 379, in U.S. Pat. No. 2,296,515 (granted Sep. 22, 1942 to Goodwin for xe2x80x9cCLUTCH PLATExe2x80x9d) and in U.S. Pat. No. 5,085,307 (granted Feb. 4, 1992 to Scheer for CLUTCH DISCxe2x80x9d).
Engagement (activation) of a friction clutch involves the establishment of an abrupt or gradual frictional contact between one friction lining of the clutch disc and the pressure plate (which rotates at the speed of the output element of the prime mover) as well as between the other friction lining and the engine-driven counterpressure plate (this counterpressure plate can constitute a simple or a composite flywheel). The friction linings slide relative to the adjacent parts (pressure plate and counterpressure plate) while the friction clutch is partly engaged, and this can result in the generation of pronounced friction heat. As disclosed in U.S. Pat. No. 2,902,130 (granted Sep. 1, 1959 to Halberg et al. for xe2x80x9cCLUTCH PLATExe2x80x9d), friction heat can cause warping or dishing of the pressure plate and counterpressure plate (flywheel) which results in a deformation causing the pressure plate to assume a conical shape. A similar (but normally less pronounced) deformation is also observable on the counterpressure plate. The just discussed deformation(s) entails or entail the development, between the friction surfaces of the pressure plate and the counterpressure plate, of a gap which widens radially inwardly or radially outwardly and is presently sought to be eliminated by resilient mounting of the friction linings on their carrier. Thus, the friction linings are mounted on the carrier in such a way that at least certain portions thereof can yield in the axial direction of the friction clutch. The afore-mentioned resilient friction lining carrier constitutes a presently preferred means for compensation of undue or excessive wear upon the component parts of the friction clutch.
Friction which develops in response to actuation (especially during engagement) of the friction clutch not only entails a pronounced wear upon the friction linings but the resulting heat also causes pronounced thermal stressing of the material of which the friction linings (and the parts supporting the friction linings) consist. Thus, the thermally induced expansion coefficients of the materials of various constituents of a friction clutch or of a clutch disc are quite different. Furthermore, all components of a friction clutch are not heated and/or cooled to the same extent when the friction clutch is actuated. All this results in pronounced deformation of various parts to a different extent due to different stresses which develop as a result of unequal heating and/or cooling.
Pronounced and non-uniform deformation of friction linings and/or of neighboring parts in a friction clutch can result, among others, in a dishing and/or axial undulation of friction linings which can be sufficiently pronounced to create problems in connection with proper operation of (such as the establishment of necessary clearances in) the friction clutch. Thus, the friction linings are not likely to become fully or adequately disengaged from the adjacent plates when the friction clutch is to be fully disengaged; this causes the friction linings to rub against the friction surfaces of the adjacent pressure plate and counterpressure plate and to cause the prime mover to transmit to the transmission so-called drag torque which is highly undesirable because it causes the generation of unnecessary wear, uneven wear, undesirable heat and other problems. The primary cause for the development of drag torque is believed to be undesirable and unpredictable heating and/or cooling of component parts of the friction clutch and the resulting bimetallic effect. Such effect can develop due to different radial expansion and different radial shifting of various parts of the friction linings and/or of their resilient lining carrier or carriers.
All in all, the overall adverse effect upon a friction clutch as a result of uneven or non-uniform heating and cooling of its components includes not only a less satisfactory or less predictable clutch engaging and disengaging action but also non-uniform wear upon the friction linings and hence a pronounced shortening of useful life of the clutch disc and/or of the entire friction clutch.
An object of the present invention is to provide a clutch disc which is less affected by changes in temperature than heretofore known friction clutches.
Another object of the invention is to provide a friction clutch wherein the constituents are connected to each other in a novel and improved way.
A further object of the invention is to provide a friction clutch which is designed in such a way that it can at least partially compensate for undesirable deformation of its constituents as a result of repeated heating and cooling due to repeated engagement, disengagement and partial engagement of the clutch.
An additional object of the invention is to provide a relatively simple and inexpensive clutch disc which can be put to use in existing types of friction clutches.
Still another object of the instant invention is to provide a friction clutch which embodies a clutch disc or clutch plate of the above outlined character.
A further object of our invention is to provide a novel and improved combination of friction linings, lining holder or carrier and cushioning spring or springs for use in a friction clutch.
Another object of the invention is to provide a novel and improved method of assembling a clutch disc for use in friction clutches and the like.
A further object of the invention is to provide a clutch disc which can stand pronounced mechanical and/or thermal stresses more reliably than heretofore known clutch discs.
An additional object of the invention is to provide novel and improved friction linings, friction lining cushions and friction lining carriers for use in the clutch discs for friction clutches.
The invention resides in the provision of a rotary clutch disc for use in friction clutches. The improved clutch disc comprises a friction facing which includes at least one annular friction lining, at least one carrier for the at least one friction lining, and torque transmitting means which serves to connect the at least one friction lining to the at least one carrier in such a way that the at least one friction lining and the at least one carrier have at least some freedom of radial movement relative to each other, i.e., movements other than radial movements are not necessarily excluded but the at least one friction lining has some freedom of radial movement relative to the at least one carrier and/or vice versa.
The arrangement can be such that at least a part of the torque transmitting means is movable within limits with the at least one friction lining relative to the at least one carrier or with the at least one carrier relative to the at least one friction lining. Alternatively, the improved clutch disc can be assembled in such a way that at least a part of the torque transmitting means is movable within limits relative to the at least one friction lining as well as relative to the at least one carrier.
In accordance with a presently preferred embodiment, the torque transmitting means includes solid and/or hollow rivets.
The at least one friction lining and/or the at least one carrier can be provided with openings and the torque transmitting means can include portions (such as the aforementioned rivets) which are received in the openings with freedom of radial movement relative to the respective openings. The portions of the torque transmitting means can be received in the openings at least substantially without play as seen in the circumferential direction of the at least one annular friction lining.
Alternatively, the at least one friction lining can be provided with first openings and the at least one carrier can be provided with second openings which register with the first openings. The torque transmitting means of such clutch disc can include first portions each of which is received with radial play in one of the first and second openings, and second portions each of which is received without radial play in the other of the first and second openings. In other words, the first and second openings of each pair of registering openings respectively receive first and second portions of the torque transmitting means.
The at least one carrier can include a resilient part and the torque transmitting means can connect the at least one friction lining to such resilient part. If the friction facing includes a plurality of friction linings, the torque transmitting means can be arranged to connect the at least one carrier with each of the friction linings. Each such friction lining can include a portion extending radially outwardly beyond the at least one carrier. The resilient part of the at least one carrier can be provided with openings, and the torque transmitting means can include components (such as the aforementioned rivets) which extend through such openings.
The at least one friction lining can include an annular reinforcing member and a friction generating part (such as a pad) which is borne by the reinforcing member. The reinforcing member can be at least partially embedded in the pad, and such reinforcing member can consist, at least in part, of sheet metal.
The at least one carrier can include an annular disc having a radially outer portion and two springs provided on the radially outer portion. The friction facing of such clutch disc can include two annular washer-like friction linings which flank the springs. At least one of these friction linings can include an annular array of arcuate segments, and the two friction linings can be disposed back-to-back.
The at least one carrier can include an annular array of first portions, and the at least one friction lining can include an annular array of second portions each of which overlies a part of or an entire first portion. The torque transmitting means of such clutch disc can include a plurality of discrete mechanical fasteners each of which connects one of the first portions to the overlapping second portion with limited freedom of movement at least substantially radially of the clutch disc. The fasteners can include rivets which form an annular array of alternating first and second rivets; the heads of the first rivets are disposed at one side and their deformed end portions are disposed at the other side of the at least one friction lining. On the other hand, the heads of the second rivets are disposed at the other side and their deformed end portions are located at the one side of the at least one friction lining, Each of the first portions is connected with the at least partially overlying second portion by a plurality of rivets and the portions of at least one of the annular arrays can consist, at least in part, of a resilient material.
The friction facing is provided with exposed at least substantially annular first and second friction surfaces which are respectively engageable by third and fourth friction surfaces provided on a pressure plate and a counterpressure plate of an engageable and disengageable friction clutch in the engaged condition of such clutch.
The at least one carrier can include a hub which is at least substantially coaxial with the at least one annular friction lining. The latter can include portions which are movable at least substantially radially of the clutch disc relative to as well as independently of each other.
The at least one friction lining of the friction facing can include at least one non-metallic portion having an exposed friction surface and at least one at least partially metallic reinforcing portion which is at least partially embedded in the at least one non-metallic portion.
The improved clutch disc or clutch plate can be utilized with advantage in friction clutches which are installed in the power trains of motor vehicles to transmit torque (when necessary) between the output shaft of the prime mover and the input shaft of the change-speed transmission.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved clutch disc itself, however, both as to its construction and the modes of assembling, installing and utilizing the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.